Silicene on Ag(111): A honeycomb lattice without Dirac bands

Mahatha, S. K.; Moras, Paolo; Bellini, V.; Sheverdyaeva, P. M.; Struzzi, Claudia; Petaccia, L.; Carbone, C.

doi:10.1103/physrevb.89.201416

Cited by 102 publications

(143 citation statements)

References 36 publications

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“…Beyond an increased background in the UV spectral region, two main effects are evident: the absence of the van Hove peak at 1.6 eV, combined with the sharpening and the redshifting of the main absorption peak to about 3.3 eV. The former fact highlights how the presence of silver deeply impacts the band structure of the adsorbed silicon, and consequently its absorbance: This finding is consistent with a strong hybridization between Ag and Si states, as previously argued [5,[7][8][9]. These effects are apparently less evident for the a-Si case, whose absorption profile (continuous blue line in Fig.…”

supporting

confidence: 77%

“…Intense efforts have been devoted to the study of the epitaxial silicene/Ag(111) system in order to elucidate the presence of massless Dirac fermion in analogy with graphene [2,3]. Although recent experiments report on the linear dispersive bands [4], strong hybridization effects have been invoked as responsible for the disruption of π and π * bands in silicene superstructures on silver [5][6][7][8][9]. In this framework, the measured ambipolar effect in silicene-based FET characterized by a relatively high mobility when Ag is withdrawn, points to a complex physics at the silicene-silver interface, demanding a deeper comprehension of its details on the atomic scale.…”

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confidence: 99%

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Optical response and ultrafast carrier dynamics of the silicene-silver interface

Cinquanta¹,

Fratesi

Conte

et al. 2015

Phys. Rev. B

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We report a combined experimental and theoretical study of the optical response of epitaxial silicene on silver. The silicene/Ag(111) ultraviolet-visible absorption spectra, which turn out to be strongly nonadditive, are analyzed in the framework of ab initio calculations. Electronic transitions involving silver states are found to provide huge contributions to the optical absorption of silicene, compatible with a strong Si-Ag hybridization. The results are independent of the specific silicene configuration and are also worked out for thin amorphous silicon. This points to a dimensionality-driven peculiar dielectric response of the two-dimensional-silicon/silver interface, which is confirmed by means of transient-reflectance spectroscopy. The latter shows a metalliclike relaxation time, hence demonstrating the effects of the strong hybridization arising in silicene/Ag (111) Recently, the integration of silicene in field-effect transistors (FET) [1] opened new challenges in the comprehension of the chemical and physical properties of this elusive two-dimensional (2D) allotropic form of silicon. Intense efforts have been devoted to the study of the epitaxial silicene/Ag(111) system in order to elucidate the presence of massless Dirac fermion in analogy with graphene [2,3]. Although recent experiments report on the linear dispersive bands [4], strong hybridization effects have been invoked as responsible for the disruption of π and π * bands in silicene superstructures on silver [5][6][7][8][9]. In this framework, the measured ambipolar effect in silicene-based FET characterized by a relatively high mobility when Ag is withdrawn, points to a complex physics at the silicene-silver interface, demanding a deeper comprehension of its details on the atomic scale.The present paper aims at elucidating the role of the Ag(111) metallic support in determining the physical properties of the Si/Ag (2D) interface, by means of optical techniques combined with theoretical calculations. In particular we show that interface states built up by mixed silicon and silver wave functions have a striking impact on the optical response of the low-dimensional Si/Ag system.

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supporting

confidence: 77%

mentioning

confidence: 99%

Optical response and ultrafast carrier dynamics of the silicene-silver interface

Cinquanta¹,

Fratesi

Conte

et al. 2015

Phys. Rev. B

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“…An electron band with a linear dispersion was found by Vogt et al [4] near aK point of silicene grown on Ag(111) and it was discussed as emission from a modified Dirac cone with a gap between π and π * bands. However, this idea has been questioned by several authors [5][6][7][8], and the linear band is instead suggested to orig-* Corresponding author: weiwa49@ifm.liu.se inate from 2D surface or interface states that appear when the silicene layer has formed. As suggested by Cahangirov et al [9], the linear dispersion found in Ref.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical determination ofσbands on (“23×23”) silicene grown on Ag(111)

2015

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Silicene, the two-dimensional (2D) allotrope of silicon, has very recently attracted a lot of attention. It has a structure that is similar to graphene and it is theoretically predicted to show the same kind of electronic properties which have put graphene into the focus of large research and development projects worldwide. In particular, a 2D structure made from Si is of high interest because of the application potential in Si-based electronic devices. However, so far there is not much known about the silicene band structure from experimental studies. A comprehensive study is here presented of the atomic and electronic structure of the silicene phase on Ag(111) denoted as (2 √ 3 × 2 √ 3)R30°in the literature. Low energy electron diffraction (LEED) shows an unconventional rotated ("2 √ 3 × 2 √ 3") pattern with a complicated set of split diffraction spots. Scanning tunneling microscopy (STM) results reveal a Ag(111) surface that is homogeneously covered by the ("2 √ 3 × 2 √ 3") silicene which exhibits an additional quasiperiodic long-range ordered superstructure. The complex structure, revealed by STM, has been investigated in detail and we present a consistent picture of the silicene structure based on both STM and LEED. The homogeneous coverage by the ("2 √ 3 × 2 √ 3") silicene facilitated an angle-resolved photoelectron spectroscopy study which reveals a silicene band structure of unprecedented detail. Here we report four silicene bands which are compared to calculated dispersions based on a relaxed (2 √ 3 × 2 √ 3) model. We find good qualitative agreement between the experimentally observed bands and calculated silicene bands of σ character.

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“…Rashba term. That allows a description of the proposed TI phase in silicene, 14,15,23,24 germanene, and stanene.…”

Section: B Resultsmentioning

confidence: 99%

“…In the 2D TI materials currently under experimental investigation, i.e., HgTe/CdTe quantum wells 11 and InAs/GaSb heterostructures, 12,13 bulk and structural inversion asymmetry both violate the axial spin symmetry of the Hamiltonian. Other promising candidate materials such as silicene 14,15 and tin films 16 also exhibit intrinsic Rashba spin-orbit coupling breaking the axial spin symmetry. Naturally, the 1D edge electrons emerging from such 2D Hamiltonians do not have a well-defined spin.…”

Section: Introductionmentioning

confidence: 99%

Spin texture of generic helical edge states

2015

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We study the spin texture of a generic helical liquid, the edge modes of a two-dimensional topological insulator with broken axial spin-symmetry. By considering honeycomb and square-lattice realizations of topological insulators, we show that in all cases the generic behavior of a momentumdependent rotation of the spin quantization axis is realized. Here we establish this mechanism also for disk geometries with continuous rotational symmetry. Finally, we demonstrate that the rotation of spin-quantization axis remains intact for arbitrary geometries, i.e., in the absence of any continuous symmetry. We also calculate the dependence of this rotation on the model and material parameters. Finally we propose a spectroscopy measurement which should directly reveal the rotation of the spin-quantization axis of the helical edge states.

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Silicene on Ag(111): A honeycomb lattice without Dirac bands

Cited by 102 publications

References 36 publications

Optical response and ultrafast carrier dynamics of the silicene-silver interface

Optical response and ultrafast carrier dynamics of the silicene-silver interface

Experimental and theoretical determination ofσbands on (“23×23”) silicene grown on Ag(111)

Spin texture of generic helical edge states

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